« iepriekšējāTurpināt »
104 REPORT OF EXPERIMENTS ON THE EXPLOSIONS OF STEAM-BOILERS. and removed. Care was taken to ascertain occur in commerce, would cause a variation that the stationary point, given in the cylin- in the fusing point. Tin has a very uniform der, was the same with that shown by the purity in commerce, the grain or stream tin naked thermometer. As some of the alloys being always accessible. The bismuth of expanded considerably on congealing, it was commerce being obtained principally from supposed that the cylinder might prevent the native bismuth, is probably not very error from the compression of the bulh of the variable.* The lead contains variable quanthermometer, but no such compression in the tities of silver, copper, and iron. The first instrument used was detected by frequent experiments were made on the fusing point, trials.
on various specimens of common tin: this As the alloys were intended for ordinary tin showed, by re-agents, a trace of iron and use, it was deemed advisable to ascertain how
of copper, as impurities.
The fusing point far the impurities of the metals, as they of grain tin is 4420 Pah.
• It is proper to state, however, that some specimens were procured, obviously obtained from the sulphuret, and contaminated with it. They were not used.
REPORT OF EXPERIMENTS ON THE EXPLUSIONS OF STEAM-BOILERS.
601.5 An attempt was next made to ascertain what effect the impurities shown by the fusing point of lead would have upon the fusing points of alloys, into which it entered. Alloys, in atomic proportions, were selected, as much was expected from them in the way of avoiding the slow passage from the liquid to the solid state, which was observed to be the property of certain mixtures of the metals. Alloys of tin and lead were therefore made in atomic proportions; first, of grain tin and the lead already spoken of, from the Paris mint; the second, of block tin and common lead. The tin was employed in multiple proportions, as being the more fusible metal, it would probably enter more largely than the other, into the composition of fusible plates for steam-boilers. The equivalent of lead is 104; of tin, 58; the first alloy was composed of the two metals, united in this proportion, the total weight of the components being about ten ounces, troy; a new equivalent of tin was next added, and
Mean, so on, through the series: the results are given in the following table.
Upon this table we remark, first, that at all the stationary points, except in the alloy of I lead to 2 tin, the metal was solid at the stationary point ; second, that although the proportion of tin varied from one to six, and even to seven, the stationary point was not changed more than 3° for the first series, and 51° for the second ; third, that in the proportion of one of lead to four of tin, a second stationary point appeared at the point at which the metal began to lose its entire Auidity, and was found in the higher parts of the series, rising with the increased proportion of the more fusible metal, with difficulty detected at times, and disappearing by agitation of the alloy ; fourth, that the tin and lead of commerce give, for the lower stationary points in the same alloys, quantities nearly the same. A comparison of the upper stationary points appears on next page.
Thermometer fell to 3650, rose rapidly to 3690, where it was stationary for a short time, then fell to 357), where it was stationary for some minutes.
Thermometer was 30 secs. in falling from 36920 to 362}, very slow: stationary at 3573 for 100 secs. No other stationary point to 200°.
Thermometer stationary at 3770, in one experiment, then fell to 358°, stationary 35 secs.: al 377 soft solid, easily penetrated, hard at lower stationary point. In another expt. fell to 3770, then rose to 3790, whence it fell rapidly to 3583°, the lower stationary point.
At 408%, a stick only pierces the surface, solid below.
Parts of the alloy liquid at stationary point.
In one experiment thermometer rose from 366] to 367°, alloy granular, semi-solid; fell to stationary point, alloy solid. By stirring, the upper point was obliterated.
In one experiment the thermometer rose half a degree from 3760, then fell rapidly to stationary point.
Thermometer rose half a degree above 38340, in one experiment, and was stationary a short time at 3814o. in another experiment; at both these times the metal was beginning to lose fluidity. Solid at lower stationary point.
Thermometer fell very slowly from 387° to 3861, and alloy began to congeal at surface.
Upper Stationary Point
382 The variable nature of the results, seems
found in alloys in definite proportions. They to point out rather the difficulty of detecting indicate that the variety of combinations in the upper point and the effect of accidental definite proportions is not considerable, if circumstances, than that it is affected mate- even it exceeds a single one; and that when rially by the impurity of the metals as found the metals are mixed in definite proportions, in commerce. This upper point rises with the alloys are in fact combinations, or mixthe proportion of the less fusible metal. The tures, of one or more chemical compounds number of degrees between it and the corre- with the metals themselves. If this be the sponding point, for the solid state of the case with alloys in which the proportions are metal shows one difficulty to be obviated in in the ratio of the equivalents or in multiple the use of the fusible alloys. For example,
ratios, it would seem to follow certainly, that the first in the table, just given, has 109° be- in alloys made in proportions not definite, the tween the point at which it begins to lose same fact would appear. That this is so, and fuidity, and that at which it is solid; the that its effects are of importance in practice, second has 111°, and the third 293° ; these will appear subsequently defects, it was hoped, would not have been
(To be continued.)
BQUATIONS FOR RAILWAY INCLINED PLANES.
The average variable velocity will be 1 (V° +116) = }(30 + 24) = 27 miles
24 per hour: also h= y + 3716=30+72
4 = v= 14 min. 77 seconds; and the
17 distance run before the velocity becomes
120 permanent is x =
6280) L, then in the event of
level be experimentally determined and found to be yi miles per hour ; th n
1 supposing the friction
of the weight 250
1 moved, then
will be the
250 force of traction. Again, suppose a plané to rise n feet per mile, the force of traction for the moving weight L will be
1 250 the pull on the horizontal plane with the
L moving weight L+-being equal to that on the ascent with the weight L, we have the equation,
250 and from ihis equation we find,
25 Assuming n = 1, 2, 3, 4, 5, &c. feet, the corresponding values of m will be 21•12, 10-56, 7:04, 5.28, 4.225, &c. Hence V°, V', V2, V3, &c. being the velocities experimentally determined on a level with the
L moving weights, L, L+ LT=,L+
I am, Sir, yours, &c.
Iver M·IVER. May 2, 1836.
THE MACKINTOSHIAN THEORY OF THE
sponding to the weight L moved up a plane rising 1, 2, 3, 4, &c. feet
mile. İn all the cases it is supposed that the steam is so regulated as to produce a maximum effect.
Suppose the full speed on a horizontal plane with a moving weight L is 30 miles per hour, and that with this speed the engine and train began to ascend a plane rising 16 feet per mile, and that it has been experimentally found on a level that the velocity due to a rise of 16 feet per
L mile, or to a weight (L+ 24 miles per hour; it is required to determine the time of ascending the plane, the average variable velocity, the point in the plane where the velocity becomes permanent, supposing the length of the plane to be 6 miles ?-See Mech. Mag. No. 661, p. 14.
Sir,—At the head of the “ Notes and Norices" in your last Number (666) there is an extract from an article in Silliman's Journal on currents in water, where it is asserted, “ that if a tub or other vessel is filled with water, and a hole made near the middle of the bottom of it to discharge it, the water will acquire a rotatory motion from west to south, or opposed to the apparent motion of the sun." The Guernsey Star remarks, “ This cannot be the effect of chance, but of natural laws constantly operating.” In the same Number of your Magazine there is a communication from a correspondent, W. B. of Nottingham, wherein he states, that he has observed, " that the common scarlet run. wer, or French bean, always twists in one direction round the stick that supports it ;” but he has not observed, or at least has omitted to state, that the direction which the scarlet runner takes is from west to south, or that opposed to the apparent motion of the sun. Again, the real motions of the planets is in the direction opposed to the apparent motion of the sun.
Whether the same law governs all these motions, and very probably many more which have hitherto escaped our notice, is what I do not pretend to determine. Whether the same natural power that moves an atom moves a world, or whether, agreeable to the “ Mackintoshian philosophy,”, electricity is the great moving principle that keeps all in life and motion, I am not philosopher enough to give an opinion; but I was
is V16 =
struck with the coincidence upon reading THE LONG-WORK SYSTEM OF MINING. the above extract, and thought it worth
Sir,-1 am greatly obliged to you for recording. There may possibly be some the information you gave me in your great law of nature peeping forth through
excellent Magazine (vol. xxiv. p. 505), this small aperture, and which, if the
with regard to the mining of coal by the opening could be dilated by a few addi
long-work system. You inform us that tional facts, might instantly emerge into the Committee came to the conclusion broad day.
that the present mode of working in the Yours, &c.
North was better than long-work, and TREVOR.
yet Mr. Buddle does not deny that long
work is the best mode of ventilating a MR. JOPLING'S RAILWAY HINTS-RAIL
mine; and Mr. Mitcheson says, the cur
rent of air passing through long-work WAY-CARRIAGE BREAK.
wonld keep it clear, and so prove an ad. Sir,-With due deference to Mr. Jop- vantage. Jing, I beg to state, that the idea of ap
Now, sir, what did the Committee plying bands or straps to locomotive.
meet and hear evidence for- was it not carriages, however new or novel, on
to get at the best mode of ventilating the railways, is not so as regards steam
coal-mines in the North of England, and, carriages on common roads, a patent
consequently, the saving of human life having been taken out by an eminent
Did not the evidence prove to them that engineer some few years ago for the pur
long-work was the safest way to work pose; I believe, however, it was never
the coal, and to subdue the gas, in the brought into practice. The smooth and
North of England collieries? Oh, but equable motion of the carriages on rail
then we have tried this and the other ways is certainly a powerful argument in
method, and we like our own best; it is favour of its adoption; as is also the in- what we have been used to from our troduction of the method used by Mr.
youth. And as to the loss of lives, we Russell in his road steam-carriages ; have been accustomed to that also, therenamely, dispensing with the crank-axle,
fore we may as well go on as we are.' and substituting either cog-wheels or
So, instead of adopling a method that wheel and pinion, thus gaining either
would convey the aimospheric air round power or speed; also taking the action
the face of the whole working, and to of the engine off the propelling-wheels in every living soul in the mine, the colliers an instant. A sort of basket, to precede
are still to be employed in holes and a train of carriages to turn any impedi
corners where no atmospheric air can ment off the railway, was proposed in approach-destruction, ready upon every the Mech. Mag. No. 404, by Sir G. change of wind or density of atmosphere, Cayley some years ago.
to be forced out into the open roads and Since the opening of the Greenwich
workings. From that moment the mise Railway, I beg to state, that I have con
called safety-lamp becomes a man-trap. templated an addition to the locomotive
Mr. Buddle in his evidence says, that carriage, in the shape of a break,* applied either to the propelling-wheels, or to the
he had tried the principle of long-work, whole four. The method is easy of adop- generally called the Lancashire system (it tion, and the mere act of shutting off the
is the Shropshire system of long-work I steam will bring the apparatus into play.
am contending for); but that induced a As I cannot, however, just now spare
double mischief-100 inuch small coal by time to make the illustrative drawings,
the weight of the top behind pressing or complete an experimental model, I
upon the face of the coal-If Mr. Bud. must, for the present, withhold further
dle's long-work had been long enough communication on the subject,
and wide enough to have brought down
am, Sir, your obedient servant,
the roof of the mine behind him, it J. ELLIOTT, Machinist.
would bave lightened the pressure on the 14, Stacey-street, Soho.
face of the coal, and instead of breaking
the coal small, would have assisted in • We have been favoured with a description of working it. “ But the chief mischief, the break now in use on this railway by the inventer, and shall give it in our next or succeeding
he says, “attending it, was the breaking Number. It is a very excellent one.-ED. M.M.
of the strata up to the yard coal-seam,